Assays for the transcript level of Ps87 during incompatible interactions. RNA samples were isolated from urediniospores, germinated urediniospores, or leaves of wheat cultivar Shuiyuan 11 inoculated with CY23 and collected at the indicated time points. The expression level of Ps87 was calculated by the comparative Ct method with the actin gene of P. striiformis f. sp. tritici as the endogenous reference for normalization. Relative quantification was computed with its expression levels in different stages in comparison to that in urediniospores. The average and standard error were calculated from three biological replicates. S, urediniospores; GS, germinated urediniospores; dpi, days post inoculation.